Portable kiln for making charcoal from forestry wood waste

ABSTRACT

A portable kiln is transported to a site of logging where there is significant wood waste. At the site, wood waste is collected. The portable kiln is assembled as it is being loaded with wood waste. Once the portable kiln is assembled it is lit with all air intakes open. When combustion is complete and charring begins, some of the air intakes are closed. When charring ends, all of the air intakes and exhausts are closed to permit the kiln to cool down.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This utility patent application claims priority from U.S.Provisional Patent Application Serial No. 60/266,661 filed Feb. 6, 2001,having the same title.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a portable kiln for makingcharcoal from forestry wood waste.

[0004] 2. Discussion of Related Art

[0005] Conventionally, charcoal is made by using either an earth pit ora brick kiln. Most of the cost in the manufacture of charcoal is thatwhich is associated with the transportation of the raw wood to thecentral processing site. For example, cut trees are transported by truckor train to a centralized processing site, where the charcoal ismanufactured.

[0006] Approximately one third of the volume of trees cut down is nottransported to the central processing site, meaning that loggers mustcut down fifty percent (50%) more trees than if the entire tree is used.Thus, more trees are cut down because the centrally located kilns do notutilize the leftover. Also, the planting of new trees is also inhibitedbecause of the abundance of wood waste.

[0007] The leftover wood is typically discarded and left on the forestfloor. While the leftover wood is still moist, new types of fungi andinsect species appear on the leftover wood, which can ruin new treegeneration and may adversely affect human health. In addition, once theleftover wood becomes dry it becomes extremely combustible. The presenceof combustible matter throughout the forest is a significant reason forincreased forest fires.

[0008] Such leftover wood turns the forest into a carbon dioxide (C02)supplier, instead of a natural “sink” that soaks up gases responsiblefor the “greenhouse” effect that causes global warming, and therebyjeopardizes the balance of the existing ecosystem. On the other hand,usable wood which is not of sufficient volume to be transported costeffectively is either disposed of or salvaged by expensive and timeconsuming techniques. However, it never gets used in a charcoal makingprocess.

[0009] The traditional method of making charcoal in an earth pitrequires several days, or even weeks, for the wood to be properlyseasoned and dried prior to being heated. Furthermore, the charcoal andby-products, which are tar and ash, can not be fully recovered becausethey all seep into the earth. Another disadvantage is that the recoveredcharcoal is often contaminated with earth and stones. Making charcoalusing this method can often take more than one week after the wood isdried.

[0010] The traditional method of making charcoal in centrally locatedbrick kilns on the other hand has no problems with loss of charcoal,because in most brick kilns tar condensation is not collected. However,brick kilns require constant supervision.

[0011] The carbonization stage may be decisive in charcoal productioneven though it is not the most expensive one. Unless it is carried outas efficiently as possible, it puts the whole operation of charcoalproduction at risk since low yields in carbonization reflect backthrough the whole chain of production as increased costs and waste ofresources.

[0012] Wood consists of three main components: cellulose, lignin andwater.

[0013] The cellulose and lignin and some other materials are tightlybound together and make up the material we call wood. The water isabsorbed or held as molecules of water on the cellulose/ligninstructure. Air dry or “seasoned” wood still contains 12 to 18% ofabsorbed water. Growing, freshly cut or “unseasoned” wood contains, inaddition, liquid water to give a total water content of about −40 to100% expressed as a percentage of the oven dry weight of the wood.

[0014] The water in the wood has to be driven off as vapor beforecarbonization can take place. To evaporate water requires a lot ofenergy so that using the sun to pre-dry the wood as much as possiblebefore carbonization greatly improves efficiency. The water remaining inthe wood to be carbonized must be evaporated in the kiln or pit and thisenergy must be provided by burning some of the wood itself whichotherwise would be converted into useful charcoal.

[0015] The first step in carbonization in the kiln is drying out of thewood at 100° C. or below to zero moisture content. The temperature ofthe oven dry wood is then raised to about 280° C. The energy for thesesteps comes from partial combustion of some of the wood charged to thekiln or pit and it is an energy absorbing or endothermic reaction.

[0016] When the wood is dry and heated to around 280° C., it begins tospontaneously break down to produce charcoal plus water vapor, methanol,acetic acid and more complex chemicals, chiefly in the form of tars andnon-condensable gas consisting mainly of hydrogen, carbon monoxide andcarbon dioxide. Air is admitted to the carbonizing kiln or pit to allowsome wood to be burned and the nitrogen from this air will also bepresent in the gas. The oxygen of the air is sued up in burning part ofthe wood charged.

[0017] The spontaneous breakdown or carbonization of the wood above atemperature of 280° C. liberates energy and hence this reaction is saidto be exothermic. This process of spontaneous breakdown or carbonizationcontinues until only the carbonized residue called charcoal remains.Unless further external heat is provided, the process stops and thetemperature reaches a maximum of about 400° C. This charcoal, however,will still contain appreciable amounts of tarry residue, together withthe ask of the original wood. The ask content of the charcoal is about 3to 5%; the tarry residue may amount to about 30% by weight and thebalance is fixed carbon—about 65 to 70%. Further, heating increases thefixed carbon content by driving off and decomposing more of the tars. Atemperature of 500° C. gives a typical fixed carbon content of about 85%and a volatile content of about 10%. The yield of charcoal at thistemperature is about 33% of the weight of the oven dry woodcarbonized—not counting the wood, which was burned to carbonize theremainder. Thus the theoretical yield of charcoal varies withtemperature of carbonization due to the change in its content ofvolatile tarry material. The following table shows the effect of finalcarbonization temperature on the yield and composition of the charcoal.

[0018] Effect of carbonization temperature on yield and composition ofcharcoal Charcoal Carbonization yield based on Temperature Chemicalanalysis of charcoal oven dry wood ° C. Of fixed charcoal % volatilematerial (0% moisture) 300 68 31 42 500 86 13 33 700 92  7 30

[0019] Low carbonization temperatures give a higher yield of charcoalbut this charcoal is low grade, is corrosive due to its content ofacidic tars, and does not bum with a clean smoke-free flame. Goodcommercial charcoal should have a fixed carbon content of about 75% andthis calls for a final carbonizing temperature of around 500° C.

[0020] The yield of charcoal also shows some variation with the kind ofwood. There is evidence that the lignin content of the wood has apositive effect on charcoal yield. A high lignin content gives a highyield of charcoal. Therefore, mature wood in sound condition ispreferred for charcoal production. Dense wood also tends to give adense, strong charcoal, which is also desirable. However, very densewoods sometimes produce a friable charcoal because the wood tends toshatter during carbonization. The friability of charcoal increases ascarbonization temperature increases and the fixed carbon contentincreases as the volatile matter content falls. A temperature of 450 to500° C. gives an optimum balance between friability and the desire for ahigh fixed carbon content.

[0021] The many variables possible in carbonization make it difficult tospecify an optimum procedure—generally the best results will be obtainedby using sound hardwood of medium to high density. The wood should be asdry as possible and usually be split to eliminate pieces more than 20 dmthick. Firewood, which will be burned up inside the kiln or pit to dryout and start carbonization of the remainder, can be of inferior qualityand temperature. One should try and reach a final temperature of around500° C. through the whole of the charge. With pits this is difficultsince the air circulation and cooling effects are irregular and coldspots occur. These produce “brands” of uncarbonized wood. Trying toreach a final overall temperature of 500° C. with a pit or kiln havingpoor and irregular air circulation usually results in burning part ofthe charcoal to ashes, while leaving other parts of the charge onlypartly carbonized. Hence the importance of using well designed kilnsproperly operated for an efficient charcoal operation.

[0022] Carbonization produces substances, which can prove harmful, andsimple precautions should be taken to reduce risks.

[0023] The gas produced by carbonization has a high content of carbonmonoxide, which is poisonous when breathed. Therefore, when workingaround the kiln or pit during operation and when the kiln is opened forunloading, care must be taken that proper ventilation is provided toallow the carbon monoxide, which is also produced during unloadingthrough spontaneous ignition of the hot charcoal, to be dispersed.

[0024] The tars and smoke produced from carbonization, although notdirectly poisonous, may have long-term damaging effects on therespiratory system. Housing areas should, where possible, be located sothat prevailing winds carry smoke from charcoal operations away fromthem and batteries of kilns should not be located in close proximity tohousing areas.

[0025] Wood tars and pyroligneous acid can be irritant to skin and careshould be taken to avoid prolonged skin contact by providing protectiveclothing and adopting working procedures which minimize exposure.

[0026] The tars and pyroligneous liquors can also seriously contaminatestreams and affect drinking water supplies for humans and animals. Fishmay also be adversely affected. Liquid effluents and waste water frommedium and large scale charcoal operations should be trapped in largesettling ponds and allowed to evaporate so that this water does not passinto the local drainage system and contaminate streams.

[0027] Fortunately kilns and pits, as distinct from retorts and othersophisticated systems, do not normally produce liquid effluent—theby-products are mostly dispersed into the air as vapors. Precautionsagainst airborne contamination of the environment are of greaterimportance in this case.

[0028] Charcoal ready for use by the consumer implies a certain sequenceof steps in a production chain all of which are important and all ofwhich must be carried out in the correct order. They have varyingincidence on production cost. Noting these differences enables theimportance of each step or unit process to be assessed so that attentionmay be concentrated on the most costly links of the production chain.

[0029] Charcoal is the solid residue remaining when wood is “carbonized”or “pyrolysed” under controlled conditions in a closed space such as acharcoal kiln. Control is exercised over the entry of air during thepyrolysis or carbonization process so that the wood does not merely burnaway to ashes, as in a conventional fire, but decomposes chemically toform charcoal.

[0030] Air is not really required in the pyrolysis process. In fact,advanced technology methods of charcoal production do not allow any airto be admitted resulting in a higher yield, since no extra wood isburned with the air and control of quality is facilitated.

[0031] The pyrolysis process once started, continues by itself and givesoff considerable heat. However, this pyrolysis or thermal decompositionof the cellulose and lignin of which the wood is composed does not startuntil the wood is raised to a temperature of about 300° Celsius.

[0032] In the traditional charcoal kiln or pit some of the wood loadedinto the kiln is burned to dry the wood and raise the temperature of thewhole of the wood charge so that pyrolysis starts and continues tocompletion by itself. The wood burned in this way is lost. By contrast,the success of sophisticated continuous retorts in producing high yieldsof quality charcoal is due to the ingenious way in which they make useof the heat of pyrolysis, normally wasted to raise the temperature ofthe incoming wood so that pyrolysis is accomplished without burningadditional wood. Although some heat impact is needed to make up for heatlosses through the walls and other parts of the equipment. Thecombustible wood gas given off by the carbonizing wood can be burned toprovide this heat and to dry the wood. All carbonizing systems givehigher efficiency when fed with dry wood since removal of water fromwood needs large inputs of heat energy.

[0033] The pyrolysis process produces charcoal which consists mainly ofcarbon together with a small amount of tarry residues, the ash containedin the original wood, combustible gases, tars, a number ofchemicals—mainly acetic acid and methanol—and a large amount of waterwhich is given off as vapor from the drying and pyrolitic decompositionof the wood.

[0034] When pyrolysis is completed, the charcoal that has arrived at atemperature of about 500° C. is allowed to cool down without access ofair. It is then safe to unload and ready for use.

[0035] The overwhelming bulk of the world's charcoal is still producedby the simple process briefly described hereunder. It wastefully burnspart of the wood charge to produce initial heat and does not recover anyof the by-products or the heat given off by the pyrolysis process.

[0036] Other woody materials such as nutshells and bark are sometimesused to produce charcoal. Wood is, however, the preferred and mostwidely available material for charcoal production. Many agriculturalresidues can also produce charcoal by pyrolysis but such charcoal isproduced as a fine powder, which usually must be briquetted at extracost for most charcoal uses. In any case, encouraging the wider use ofcrop residues for charcoal-making or even as fuel is generally an unwiseagricultural practice although the burning of sugar cane bagasse toprovide heat in sugar production and the burning of cornstalks andcoarse grasses as domestic fuel in some regions do provide an overallbenefit where carried out as part of a national agricultural policy.

[0037] On the grounds of availability, properties of the finishedcharcoal, and sound ecological principles wood remains the preferred andmost widely used raw material and there appears to be no reason why thisshould change in the future. Charcoal making can be divided into severalstages or unit operation. They are: growing the fuel wood, woodharvesting, drying and preparing the wood for carbonization, carbonizingthe wood to charcoal, screening storage and transporting to warehouse ordistribution points.

[0038] It would be desirable to provide a method and apparatus formaking charcoal in a mobile, potable kiln unit that can use all woodwaste cost effectively. It is a further object of this invention toprovide a method and apparatus for making charcoal in a mobile, portablekiln unit with minimal need for supervision. It is a further object ofthis invention to provide a method and apparatus for making charcoal ina mobile, portable kiln unit in all environmental settings.

SUMMARY OF THE INVENTION

[0039] One aspect of the invention resides in a mobile kiln for makingcharcoal from wood waste. The kiln is transported to a forested areathat is being, or recently has been logged. The wood waste employed isany part of a cut tree that has not been transported, including portionsof the tree trunk, large branches, small branches, bark and peat. Thekiln, which in its preferred embodiment includes of three main parts—abottom cylinder, an upper cylinder and a cover—is assembled while beingloaded with the wood waste. The kiln can be placed on the ground or on avehicle, such as a flat bed truck. Once the kiln is assembled andfilled, the wood is consumed to make charcoal. During the carbonizationprocess, the kiln can be transported. Once the carbonization process iscompleted, the kiln can be easily emptied of both the charcoal andbyproducts.

[0040] Another aspect of the present invention is a method for preparinga portable kiln to turn wood waste into a charcoal, which is comprisedof the steps of transporting the unassembled portable kiln to a site ofwood waste, assembling the portable kiln by placing a base on a flatarea, placing loose earth or sand around the base, placing air channelsradially around the base, and filling the base with wood waste so as toavoid blocking the air channels with wood waste. A further aspect ofthis method may include use of a bottom section and an upper section toconstitute the base, wherein the bottom section is filled with woodwaste, the upper section is secured to the bottom section, and then itis also filled with wood waste. The kiln can then be lit to transformthe wood into charcoal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] For a better understanding of the present invention, reference ismade to the following description and accompanying drawings, while thescope of the invention is set forth in the appended claims.

[0042]FIG. 1 is an elevation view of the portable kiln in an unassembledcondition on a trailer vehicle equipped with a crane.

[0043]FIG. 2 is an exploded view of the portable kiln of FIG. 1.

[0044]FIG. 3 is atop view of the bottom section of the portable kiln ofFIG. 1, but with waste wood stacked inside.

[0045]FIG. 4 is a side view of the bottom section of FIGS. 2 and 3.

[0046]FIG. 5 is a cross-section across 5-5 of FIG. 2.

[0047]FIG. 6 is a cross-section across 6-6 of FIG. 2.

[0048]FIG. 7 is a cross-section across 7-7 of FIG. 2.

[0049]FIG. 8 is a cross-section across 8-8 of FIG. 2.

[0050]FIG. 9 is a cross-section across 9-9 of FIG. 2.

[0051]FIG. 10 is a front view of handles.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0052] A portable kiln unit arrives at a forest or other logged site forprocessing the wood waste that remains that the site. Wood waste includeanything from unused tree trunks to small branches, bark, peat and nuts.The portable kiln unit may be transported via a flat top truck or a flatbed trailer.

[0053] As can be seen in FIGS. 1 and 2, the portable kiln includes abase and a lid. The base may include a plurality of sections, such as abottom section 10 and an upper section 20. The lid may be a unitarycover 30 or be made of a plurality of segments joined together. Thebottom section 10 and the upper section 20 may be of any geometricshape, such as cylindrical. If cylindrical, the cover 30 may be conical.Otherwise, the cover 30 preferably converges upwardly as it extends fromthe upper section 20. Each section is preferably made from a sheetmetal. The kiln can be transported to a site atop a flatbed trailer 50that is equipped with a crane 60 in either an unassembled condition(FIG. 1) or an assembled condition (FIG. 2).

[0054] In the unassembled condition of FIG. 1 for transport, the bottomsection 10 and upper section 20 are nested together by inserting theupper section 20 into the bottom section 10. The cover 30 is positionedinside of the upper section 20, such that it is firmly wedged andsecured against slippage. Preferably, the nested bottom section, uppersection 20 and cover 30 are arranged on a flatbed trailer 50 or flatbedtruck, preferably large enough to accommodate more than one portablekiln.

[0055] The bottom section 10 has an upper inward shelf 12 (FIG. 5) and alower outward shelf 14 (FIG. 6), both having a right angle secured to awall of the bottom section 10. The upper section 20 has an upper inwardshelf 22 (FIG. 5) that has a right angle secured to a wall of the uppersection and a reinforcement panel 24 (FIG. 7) that is straight inalignment with the wall of the upper section 20. The reinforcement panel24 reinforces and strengthens the lower portion of the wall of the uppersection 20.

[0056] The cover 30 has an inward shelf 32 that is right angled, butwith its lower part protruding inwardly beneath a lower perimeter of thecentral portion of the cover 30. The cover 30 may be equipped withhandles 34 (FIGS. 1,2,10) to enable lifting with the crane 60 or enablemanual movement of the cover 30.

[0057] Preferably, the cover 30 is conical with four exhausts 40equidistant between their neighbors. Each exhaust includes an steamrelease port 44 into which is fitted a steam cover 42. The steam cover42 is elongated with a ring projecting from its middle region. The ringrests upon a protruding edge of a hole in the cover 30 that is boundedby the steam release port 44 (see FIG. 9).

[0058] In the unassembled condition on a flatbed trailer or truck, thecover 30 is arranged with its open bottom on the flatbed and within theconfines of the upper section 20. The upper inward rim 22 of the uppersection is above the conical top of the cover 30. The upper section 20is within the confines of the bottom section 10, whose upper inward rim12 is arranged above the upper inward rim 22.

[0059] To assemble the unassembled portable kiln, the crane 60 may beused to remove each section of the portable kiln separately. The uppersection 20 is to be stacked on the upper inward shelf 12 of the bottomsection 10. The inward shelf 32 of the cover 30 is to be stacked on theupper inward shelf 22 of the upper section 20. Whether unassembled yetnested (FIG. 1) or assembled (FIG. 2), the portable kiln uses the samefloor space on the flatbed trailer. As should be apparent, the insidediameter of the bottom section 10 is larger than the outside diameter ofupper section 20 and larger than the outside diameter of the inwardshelf 32 of the cover 30.

[0060] The kilns can be easily transported using a flat-bed truck orflat-bed trailer 50 (see FIG. 1). To transport the kiln in the back of apick-up vehicle, the two sections 10, 20 can be nested together byinserting the upper section 10 into the lower rim of the bottom section20 and rolled onto the back of the vehicle using a wooden ramp. Thecover 30 can be positioned inside the nested sections 10, 20 and theload should be firmly wedged and tied to prevent rolling.

[0061] Care must be taken when unloading the sections 10,20 fromvehicles. If the sections 10, 20 are dropped onto their sides, thendistortions are likely and difficulties will be encountered whenattempts are made to assemble the sections 10, 20 during use. Slightdistortion can be tolerated but severe distortion should be correctedusing a car jack and two lengths of timber inserted across the diameterof the damaged section.

[0062]FIG. 2 also shows a plurality of air channels 80, each with asupporting collar 82 onto which may be fitted a smokestack 90. Each airchannel 80 includes a horizontal portion that is hollow with oppositeends that are open and an opening between the opposite ends that is incommunication with the interior hollow space defined by the supportingcollar 82.

[0063] For economy of labor, two or more kilns may be operated as agroup within reasonable walking distance of each other. This enablesoperators to unload and load one unit when the other kilns are in thecarbonization or cooling stage.

[0064] To avoid the unnecessary carrying of wood, the kilns shouldfrequently be rolled to new sites adjacent to the wood supply. Theindividual sections of the kiln can be rolled by two or three men,usually with two men pushing from behind and one main guiding thesection from the front. Wooden levers are recommended for tipping theindividual sections onto their sides prior to rolling them to a newposition. Rolling the sections is far easier than sliding themhorizontally, even where distances of only 1 or 2 meters are concerned.The task of manipulating these kilns on the forest floor becomesconsiderably easier with experience.

[0065] Choosing a flat area on the forest floor is recommended. Awell-drained and roughly leveled area, approximately 3 meters indiameter, should be chosen, in close proximity to the wood supply. Treestumps and large root systems should be avoided and excessiveundergrowth should be removed from the chosen area and the ground madefirm by stamping it down. Loose earth or sand should be available closeto the site for sealing off the air supply to the kiln during operation.A sandy or loamy soil is preferred and, if not available, a supply ofsand should be obtained from a nearby stream for the initial operations.This material can be re-used and will soon increase in volume ascharcoal dust and wood ash, produced during successive operations, areincorporated into it.

[0066] The wood should be felled, cut up and stacked at least threeweeks before kilning, if the maximum yield of charcoal is to beobtained. Dry wood needs less charring time and increases the conversionefficiency of the process. The size of wood most suitable is between 450to 600 mm long and up to 200 mm in diameter. Branches up to 900 mm longcan be included provided their diameters preferably do not exceed 130 mmand the packing density in the kiln is not markedly reduced. Logs withdiameters approaching 300 mm may be used provided they are cut intolengths no greater than 300 mm. Wood with a diameter greater than 300 mmshould be split before use.

[0067] Branches with a diameter of less than 40 m should not be mixed inthe same charge with timber of maximum diameter. This material should becharged with other small to medium size wood. Approximately 7 stackedcubic meters of wood are required to fill the kiln.

[0068] Tools required for a 2 or 3 man operation of the kiln: Chainsawor crosscut saw Wooden pole or plank 2 shovels or spades Sieve chuteCutlass Sacks Axe Sledge hammer Needles and string 2 Wedges Heat proofgloves

[0069] The assembly and loading of the kiln is completed as follows. Thebottom section 10 of the kiln is rolled onto the prepared site andlowered into its operating position. Using a wooden pole as a lever theeight-air inlet channels are inserted open side down radially underneaththe bottom section at equidistant intervals. Equal spacing will beeasily achieved f the first four channels are inserted at 90° intervalsand the remaining four inserted between them.

[0070] Each air channel 80 should protrude a minimum of 250 mm into thekiln to prevent overheating of the kiln wall. The supporting collar 82on the top of the channel should not lean inwards towards the kiln wall,otherwise it will be difficult to position the chimneys once the kilnhas been assembled. When the inlet-outlet air channels 80 are inposition, it is necessary to check that they are completely clear of anyobstruction.

[0071] The bottom of the kiln is loaded with wood making sure that theends of the inlet/outlet air channels 80 and the spaces between them arenot blocked. To achieve this, the charge is supported on “stringers”which are medium diameter (150 mm) pieces of cordwood arranged radiallylike the spokes of a wheel.

[0072] At each quadrant of the kiln's base dry kindling wood, togetherwith any inflammable waste (paper, sump oil, etc.) is placed between thestringers from the edge of the bottom of the kiln to the center toprovide four lighting points.

[0073] A bridge of small/medium diameter wood and branch (incompletelycharred wood from a previous firing) is now placed across the stringersover the kindling in the shape of a cross. Bridging the remainingexposed stringers with small/medium diameter wood completes the baselayer of the kiln.

[0074] By supporting the first layer of wood above the ground onstringers, air ducts are formed under the charge, which will allow thedire to spread more rapidly into the center of the kiln.

[0075] The bottom section 10 of the kiln is loaded with successivelayers of wood 70, filling in the vacant space as much as possible andplacing the larger diameter timber towards the center of the kiln. Whenthe bottom section 10 is full and all the joint surfaces of the kiln arescraped clean, the upper section 20 is rolled alongside. The uppersection 20 is then pushed up on to the supporting shelf 12 of the bottomsection 10.

[0076] The loading of wood 70 is continued until the charge forms aconical shape above the rim of the upper section 20 but, at the sametime, will allow the cover 30 to be located into the rim withouthindrance. The cover 30 is then rolled alongside the kiln and pushed uponto its supporting shelf 22. Two experienced men can load the kiln inabout two hours.

[0077] After ensuring that all four steam release ports 44 in the cover30 are open, a flame is applied to the four lighting points. Where thereis a prevailing wind, the area of the kiln on the windward side willburn more quickly. To allow for this, the lighting points facing thewind are not lit until the lee side of the kiln is well alight.

[0078] The kiln is allowed to burn freely for about 30 minutes until thebottom section at each lighting point becomes so hot that it isunpleasant to stand close to the kiln. During this period, copiousamounts of steam will be released from the four steam release ports 44in the cover 30 of the kiln. While this is in progress the jointsbetween the bottom and upper sections 10, 20 of the kiln are filled withsand or soil and the four smoke stacks are placed into position over thesupporting collars 82 of each alternate air channel 80.

[0079] As each sector of the kiln reaches the required temperature, thespaces between the inlet/outlet air channels 80 are covered with sand orsoil. When all the spaces between the channels have been covered, theopen ends of the four channels supporting the smokestacks 90 are sealed.The steam release ports are now closed so that the smoke is drawn out ofthe base of the kiln by the four smokestacks 90. When the drought hasbeen reduced, air enters the kiln only through the inlet channels fromwhere it flows up through the center of the charge. The combustion gasesare drawn down the outer edge of the kiln and are released through thesmokestacks 90. As the air and exhaust gases flow in oppositedirections, this condition is known as the reverse drought.

[0080] Each smokestack 90 should emit a column of thick white smoke15-30 minutes after promoting the reverse drought. Throughout the periodof carbonization it is advisable to ensure that even temperatures aremaintained around the circumference of the kiln. Control is easier whenthe kilns are operated in sheltered positions. If there is a strongprevailing wind, the temperature profile across the kiln may becomeunbalanced and it will then be necessary to partially or completelyblock one or two of the air inlets on the windward side. When operatingin wet conditions, or with freshly felled wet wood in windy conditions,more extreme efforts may be necessary to balance the kiln during theinitial stages of carbonization. Under these conditions large quantitiesof water will evaporate from the soil and wood on the hottest side andcondense in the cooler regions of the kiln. This water is likely toquench any fires remaining in the lighting points and will furtherdepress the temperature in these areas.

[0081] To correct this situation the air inlets on the hot side of thekiln should be temporarily blocked and the spaces between theinlet/outlet channels on the cooler side uncovered to allow more air toenter this region of the kiln. This action will draw the fire over tothe cooler side of the kiln and, once the temperature in this area hasbeen sufficiently increased, the spaces between the channels may beresealed. After this, the normal method of controlling the supply of airto the kiln can be followed.

[0082] The burning kiln should never be left unattended when the spacesbetween the inlets/outlets channels needs to be unsealed for whateverreason above described. Serious damages to the kiln could result fromsuch behavior.

[0083] When wet wood is used or when the kiln is operated under wetconditions, the charring period is likely to be extended up to a totalof 48 hours. Because of the increased amount of wood burned internallyto drive off the excess moisture, lower yields of charcoal are to beexpected.

[0084] During charring, a certain amount of tar is deposited in theoutlet channels and smokestacks 90. This tar restricts the exhaust gasflow from the kiln and should be removed when there is a noticeablereduction in the quantity of smoke issuing from any of the stacks. Toachieve this, the stack is lifted off the supporting collar of theoutlet channel using a pair of heat proof gloves or an old sack and anyobstruction inside the smokestack 90 is removed. At the same time a longstick should be inserted through the channel into the center of the kilnto ensure that there is no internal restriction.

[0085] Some time during the carbonization period (usually 8-10 hoursafter lighting), the smoke stacks 90 should be moved onto the adjacentair channels to convert air inlets to smoke outlets and vice versa. Thiscreates a more even burn and reduces the formation of ash at the regionswhere air enters the kiln.

[0086] Charring is complete when the color of the smoke from allsmokestacks 90 takes on a bluish tinge and becomes almost transparent.This normally occurs about 16 to 24 hours after lighting. At this stagethe whole surface of the kiln should be very hot (150-200° C.) so that aspot of water applied to the wall of the kiln will evaporate immediatelywith a spitting noise. When this stage is reached the kiln is completelysealed for cooling.

[0087] Removing the smokestacks 90 and completely blocking all airchannels 80 with soil or sand seals the kiln. If necessary, additionalsoil or sand is added to the joints of the sections 10, 20 and cover 30of the kiln and the steam release ports 44 to ensure that they are fullysealed and that no air may enter. The kiln is allowed to cool forbetween 16 and 34 hours before opening and unloading. Cooling will begreatly assisted if rain falls.

[0088] Unloading the kiln is effected as follows. The kiln must not beopened until the contents are cold and the outside surface of the kilnis cool to the touch. The action of direct sunlight could obscure thisand the temperature of the inside of the kiln can be more easilyassessed by feeling the surface of the bottom section in an area shadedfrom the sun. Following this the temperature of the remaining surface ofthe lower section should be assessed to ensure that no “hot-spots”exist. If the contents of the kiln are still hot after a cooling periodof 24 hours, in this case it looks like the complete sealing from theoutside air has not been effected and an effort must be made to achievethis. Furthermore, if the kiln is opened and part of the charcoal isseen to be still alight, the kiln must be resealed for a further coolingperiod.

[0089] During carbonization the wood will have been reduced to abouthalf its original volume and it will be possible to remove the cover andtop section once the kiln has cooled, leaving the charcoal in the lowersection.

[0090] The cover 30 is removed with a minimum effort by lifting one sidefrom its supporting shelf 22 and inserting the end of a long branch orplank into the resulting gap. This piece of wood can then be used as aramp on which the cover is slid gently to the ground. The same method isused to remove the top section of the kiln.

[0091] To remove the bottom section 10, the inlet/outlet air channels 80are first removed from one side of the kiln using a lever. By applyingthe lever to the opposite side, the bottom section 10 can be tipped ontoits side, leaving the charcoal free to be loaded into sacks. A bucket ofwater or a quantity of sand or soil should be on hand while unloadingthe kiln in order to quench any small fires.

[0092] To speed up the bagging of charcoal, a sieve chute should be usedto separate the large charcoal pieces from the fines and dust.

[0093] The bottom section 10 may be positioned on the leeward side ofthe charcoal and used to support the sieve chute. This will not onlyincrease the stability of the sieve but will reduce the amount of dustreaching the operator.

[0094] If required, a free standing sieve chute can also be used. Twomen can unload it and fill the sacks with charcoal in about an hour.

[0095] As an alternative method of operation, lighting the kiln from thetop is a method, which is particularly suitable for the carbonization ofsmall wood or coconut shells, as it ensures a sufficient gas flowthrough the charge.

[0096] The kiln is loaded as previously described, without kindlingbetween the stringers at the base. The kindling wood is placed insteadin a depression 250 mm deep on top of the charge, which is then coveredwith a final layer of wood.

[0097] When carbonizing coconut shells, the use of stringers is notrequired. Care must be taken to ensure that the shell material does notblock the ends of the inlet/outlet channels inside the kiln. To achievethis, a flat piece of wood (for example, a piece of rib from a dead palmfrond) is placed on top of the end of each channel before covering itwith shells.

[0098] The fire is lit at the top through one of the four-steam releaseports and the charge is allowed to burn with a completely free access ofair into the base of the kiln. The smoke will escape through the fourports in the cover. This stage is allowed to continue for about twohours until the whole of the top section of the kiln is too hot to touchwith bare hands.

[0099] When the upper section 20 is sufficiently hot, the spaces betweenthe inlet/outlet air channels 80 are covered with sand or soil and thesmokestacks 90 are placed in position. The steam release ports 44 aresealed, such as with steam covers 42. The reverse drought and control ofthe supply of air to the kiln are achieved as in the normal method ofoperation described previously.

[0100] A suggested 5-day week work plan is outlined below. Modificationscan be made to this schedule to allow for variations in daily workinghours and a 6-day working week. Moreover, if arrangements can be madefor someone living near to the production area to undertake a half-hourperiod of light duty to seal the kiln during the weekend, then extraoperations can be achieved. Monday 08.00-10.00 Kiln 1 and Kiln 2 Unloadboth kilns. 10.00-12.00 Kiln 1 Load kiln with wood. 12.00-13.00 Kiln 1Light kiln and reduce drought 13.00-17.00 Kiln 1 Control charring.Change and clean stacks at 16.30. Kiln 2 Load kiln with wood. Tuesday08.00-08.30 Kiln 1 Change and clean stacks 08.30-11.00 Prepare wood forfuture operations 11.00-12.00 Kiln 2 Light kiln and reduce drought Kiln2 Control charring. Change and clean stacks at 16.30. Kiln 1 Shut downkiln when charring is complete Prepare wood for future operationsWednesday 08.00-08.30 Kiln 2 Change and clean stacks 08.30-14.00 Preparewood for future operations 14.00-15.00 Kiln 1 Unload charcoal from kiln15.00-17.00 Kiln 1 Start loading kiln with wood Kiln 2 Shut down kilnwhen charring is complete Thursday 08.00-10.00 Kiln 1 Finish loadingkiln with wood 10.00-11.00 Kiln 1 Light kiln and reduce drought11.00-13.00 Kiln 2 Unload charcoal from kiln Kiln 1 Control charring13.00-15.00 Kiln 2 Load kiln with wood Kiln 1 Control charring15.00-16.00 Kiln 2 Light kiln and reduce drought 16.00-17.00 Kiln 1Change and clean stacks Kiln 2 Control charring Friday 08.00-09.00 Kiln1 and Kiln 2 Change and clean stacks 09.00-13.00 Kiln 1 Shut down kilnwhen charring is complete Prepare wood for future operations Kiln 2Change and clean stacks at 12.30 13.00-17.00 Prepare wood for futureoperations Kiln 2 Close down kiln when charring is complete.

[0101] The following seven precautions should be taken to avoid problemswith operation of the kiln.

[0102] Make sure to insert the inlet/outlet channels sufficiently underthe lower rim of the bottom section of the kiln during assembly. Thehigh temperature produced at the inner end of the air channel causesserious damage to the kiln wall if the required distance between the hotzone and the kiln wall is not maintained.

[0103] Make sure to achieve sufficient gas flow through the system bynot removing deposits of tar from the outlet air channels 80 andsmokestacks 90. This results in low kiln temperatures and prolongedcharring periods.

[0104] Avoid excessive periods that are allowed for cooling the kiln,which reduce the number of operations possible in the working week.

[0105] Avoid being reluctant to move the kiln closer to the availablewood supply, because the failure to do so results in a waste of time andeffort in carrying the wood to the kiln.

[0106] Make sure that is a sufficient supply of wood available in thearea adjacent to the kiln for loading immediately when the previousoperation has been completed.

[0107] Avoid the practice of allowing large fires to develop next to thesurface of the wall of the kiln during the lighting stage. This usuallyrestricts the flow of air under the kiln and prevents the fire spreadingquickly to the center of the charge. It can also cause serious damage tothe kiln wall. Once the prepared kindling has been ignited inside thekiln, a maximum flow of air is all that is normally required.

[0108] Avoid the laborious and time-consuming practice of hand pickingthe charcoal into sacks instead of using shovels and a sieve. Excessivetime spent on unloading the kiln causes a delay in loading and lightingthe next operation.

[0109] The weight of charcoal produced in each batch operation of atransportable metal kiln is related to several physical factors. Themain factors which contribute towards maximum yields are:

[0110] high timber density

[0111] low moisture content of wood

[0112] dry operating conditions and a dry well-drained site for the kiln

[0113] high packing density of charge obtained with regular size andshape of raw material

[0114] In practice, it is seldom that all of these conditions can bearranged and consequently the yields and conversion efficiencies mightvary to a considerable degree.

[0115] The quality of charcoal is defined by various properties andthrough all are interrelated to a certain extent, they are measured andappraised separately. These various quality factors are discussed asfollows.

[0116] Moisture Content. Charcoal fresh from an opened kiln containsvery little moisture, usually less than 1%. Absorption of moisture fromthe humidity of the air itself is rapid and there is, with time, a gainof moisture, which even without any rain wetting can bring the moisturecontent to about 5 to 10%, even in well-burned charcoal. When thecharcoal is not properly burned or where pyroligneous acids and solubletars have been washed back onto the charcoal by rain, as can happen inpit and mound burning, the hygroscopitity of the charcoal can rise to15% or even more.

[0117] Moisture is an adulterant, which lowers the calorific or heatingvalue of the charcoal. Where charcoal is sold by weight, keeping themoisture content high by wetting with water is often done by dishonestdealers. The volume and appearance of charcoal is hardly changed byaddition of water. For this reason bulk buyers of charcoal prefer to buyeither by gross volume, e.g. in cubit meters, or to buy by weight anddetermine by laboratory test the moisture content and adjust the priceto compensate. In small markets sale is often by the piece.

[0118] It is virtually impossible to prevent some accidental rainwetting of charcoal during transport to the market but good practice isto store charcoal under cover even if it has been bought on a volumebasis, since the water it contains must be evaporated on burning andrepresents a direct loss of heating power. This occurs because theevaporated water passes off into the flue and is rarely condensed togive up the heat it contains on the object being heated in the stove.

[0119] Quality specifications for charcoal usually limit the moisturecontent to around 5-15% of the gross weight of the charcoal. Moisturecontent is determined by oven drying a weighed sample fo the charcoal.It is expressed as a percentage of the initial wet weight.

[0120] There is evidence that charcoal with a high moisture content (10%or more) tends to shatter and produce fines when heated in the blastfurnace, making it undesirable in the production of pig iron.

[0121] Volatile matter other than water. The volatile matter other thanwater in charcoal comprises all those liquid and tarry residues notfully driven off in the process of carbonization. If the carbonization sprolonged and at a high temperature, then the content of volatile islow. When the carbonization temperature is low and time in the kiln isshort, then the volatile matter content increases.

[0122] These effects are reflected in the yield of charcoal producedfrom a given weight of wood. At low temperature (300° C.) a charcoalyield of nearly 50% is possible. At carbonization temperatures of500-600° C. volatile are lower and retort yields of 30% are typical. Atvery high temperatures (around 1000° C.) the volatile content is almostzeroed and yields fall to near 25%. As stated earlier, charcoal canreabsorb tars and pyroligneous acids from rain-wash in pit burning andsimilar processes. Thus the charcoal might be well burned but have ahigh volatile matter content due to this factor. This causes anadditional variation in pit burned charcoal in wet climates. Thereabsorbed acids make the charcoal corrosive and lead to rotting of jutebags—a problem during transport. Also it does not burn cleanly.

[0123] The volatile matter in charcoal can vary from a high of 40% ormore down to 5% or less. It is measured by heating away from air, aweighed sample of dry charcoal at 900° C. to constant weight. The weightloss is the volatile matter. Volatile matter is usually specified freeof the moisture content, i.e. volatile matter—moisture or(V.M.—moisture).

[0124] High volatile charcoal is easy to ignite but may burn with asmoke flame. Low volatile charcoal is difficult to light and burns verycleanly. A good commercial charcoal can have a net volatile mattercontent—(moisture free) of about 30%. High volatile matter charcoal isless friable than ordinary hard burned low volatile charcoal and soproduces fewer fines during transport and handling. It is also morehygroscopic and thus has a higher natural moisture content.

[0125] Fixed Carbon Content.

[0126] The fixed carbon content of charcoal ranges from a low of about50% to a high or around 95%. Thus charcoal consists mainly of carbon.The carbon content is usually estimated as a “difference”; that is tosay, all the other constituents are deducted from 100 as percentages andthe remainder is assumed to be the % of “pure” or “fixed” carbon. Thefixed carbon content is the most important constituent in metallurgysince it is the fixed carbon which is responsible for reducing the ironoxides of the iron ore to produce metal. But the industrial user muststrike a balance between the friable nature of high fixed carboncharcoal and the greater strength of charcoal with a lower fixed carbonand higher volatile matter content to obtain optimum blast furnaceoperation.

[0127] Ash Content.

[0128] Ash is determined by heating a weighed sample to red heat withaccess of air to bum away all combustible matter. This residue is theash. It is mineral matter, such as clay, silica and calcium andmagnesium oxides, etc. present in the original wood and picked up ascontamination from the earth during processing.

[0129] The ash content of charcoal varies from about 0.5% to more than5% depending on the species of wood, the amount of bark included withthe wood in the kiln and the amount of earth and sand contamination.Good quality lump charcoal typically has ash content of about 3%. Finecharcoal may have a very high ash content but if material less than 4 mmis screened out the plus 4 m residue may have an ash content of about 5to 10%. Buyers naturally suspect fine charcoal and it is difficult tosell (and use, unfortunately).

[0130] Typical charcoal analysis found in our production in Africa.Moisture Volatile Fixed Gross Wood content Ash matter Carbon CalorificSpecies % % % % value KJ/kg Oak 3.5 2.1 13.3 81.1 32,500 Coconut 4.0 1.513.5 83.0 30,140 Shell

[0131] In an area of vast logging, there may be sufficient wood wastefor the running of several cycles or one or more transportable kilns.Upon arriving at a logging site that will require more than one kilncycle, the kiln should be placed in a flat area with at least the samediameter as the bottom section. In a preferred embodiment, the diameterof the bottom section 10 is three (3) meters. Loose earth or sand shouldbe placed at the bottom of the kiln. The bottom section 10 and uppersection 20 can be shifted to their side and then rolled to the desiredarea. In areas which do not require more than one kiln cycle, or, forthe last kiln cycle in an area requiring multiple kiln cycles, the kilncan be assembled on the flatbed trailer, allowing the kiln to continueits cycle as it is transported to the next available site.

[0132] Once the bottom section 10 is placed in the desired location, airchannels 80 (FIG. 3) are placed beneath and radially around the bottomsection 10 (FIG. 4). The air channels 80 should be placed at equidistantintervals and protrude into the bottom section 10 to prevent overheatingof the portable kiln's walls. In the preferred embodiment, the airchannels 80 protrude into the bottom section 10 to a distance that isabout 0. 028 of the diameter of the bottom section 10.

[0133] After the air channels 80 are arranged, the bottom section 10 isthen loaded with the available wood waste. The length of the individualpieces of wood waste, for instance branches, is limited by the diameterof the bottom section 10. For optimal charcoal creation, the diameter ofthe pieces of wood waste should not be greater than one third of thediameter of the bottom section 10. The loading of the wood waste intothe bottom section 10 should be done in such a way that the air channels80 are not blocked. This is accomplished by placing larger pieces ofwood waste, called “stringers,” which typically include branches orportions of a trunk with a diameter which is of a similar size to theprotrusion of the air channels 80, radially throughout the base of thebottom section 10. The air channels 80 have supporting collars 82 thatextend vertically outside the bottom section 10.

[0134] Thereafter, at each quadrant of the bottom section 10, in betweenthe stringers, dry kindling wood, together with inflammable waste, isplaced between the stringers. These areas of dry kindling wood providethe lighting points. Once the lighting points are established, small ormedium diameter wood waste is then placed across the stringers in theshape of a cross. Once the cross is laid down, small or medium diameterwood waste should be used to bridge the remaining exposed stringers.This method of creating a first layer of wood on stringers forms airducts underneath the bottom layer of wood, thereby allowing the fire tospread more rapidly into the center of the kiln.

[0135] The bottom section 10 is then filled with wood waste 70. Toobtain optimal results, the larger diameter wood waste 70 is placedtowards the center. Once the bottom section 10 is filled with woodwaste, the base of the upper section 20 is placed on top of the upperinward shelf 12. The outside diameter of the upper section 20 is smallerthan the inside diameter of the bottom section 10. Because the upperinward shelf 12 is below the upper edge of the bottom section 10, thebase of the upper section 20 is held within the bottom section 10.

[0136] Once the upper section 20 is supported by the bottom section 10,the upper section is filled with wood waste. The wood waste 70 is loadedinto the upper section 20, such that the top of the load is conical inshape, whereby the outer edges of the load are below the upper inwardrim 22 of the upper section 20, and the top of the load rises above thetop of the upper section 20.

[0137] Once the upper section 20 is completely loaded, the cover 30 isplaced on top of the upper section 20. The outside diameter of the cover30 is slightly smaller than the inside diameter of the upper section 20.Because the upper inward rim 22 is below the upper edge of the uppersection 20, the lower portion of the cover 30 is held within the uppersection 20. The cover 30 (FIG. 6) also contains four steam release ports44. The steam release ports 44 are left open during the combustion andcharring process, but closed after the charring process is complete.

[0138] Seams between the upper and lower sections, between the uppersection and the cover, and between the lower section and the base shouldbe sealed to prevent air flow. This sealing may be effected in a costeffective manner by covering the seams with sand of dirt or othersealing material, such as a heat resistant paste or compound.

[0139] When the portable kiln is loaded and assembled, the steam releaseports 44 are open and all the air channels 80 are open. A flame is thenapplied to the four lighting points of the dry, smaller size kindlingwood within the periphery of the kiln towards the bottom. The kiln isthen allowed to burn freely. After 5-10 minutes, smokestacks 90 areerected at every other one of the air channels 80, by securing avertically directed tubular smokestack 90 onto a supporting collar 82that is outside of the kiln. Each smokestack 90 may be of a height thatreaches an elevation higher than the apex of the cover 30 and isapproximately the same diameter as that of the diameter of thesupporting collar 82.

[0140] In the event that seams between the upper and lower sections 10,20 and between the upper section 20 and the cover 30 are not sealed,smoke may emerge through them. Any such smoke emerging through the seamssignifies the need to add more sand or dirt or other sealing paste orcompound to the seals at locations where the smoke emerges until thesmoke no longer emerges through the seams.

[0141] Once the kiln reaches a temperature of approximately 100 degreescentigrade and kept at that temperature for thirty (30) minutes, thesteam release ports 40 are closed and the kiln remains at 150 to 200degrees centigrade for approximately 12-16 hours, while the wood wastechars. Charring is complete when the smoke coming out through the inletstakes on a bluish tinge. At that time, all of the air channels aresealed, and the kiln is allowed to cool for approximately 8-10 hoursdepending upon the atmospheric temperature outside, before it is openedand unloaded. The kiln is opened when the kiln is cool to the touch.

[0142] Although the preferred embodiment employs four steam releaseports 44 in the cover 30, the present invention envisions the use of anynumber of ports, even if only one is used. Further, although thepreferred embodiment employs eight air channels 80 and four smokestacks90, any number of air channels and smokestacks may be used. Forinstance, the four inlet air channels 80 may be joined together to sharea common air intake header. Also, the four smokestacks may be joined toshare a common exhaust chimney. Furthermore, various sensors anddetectors may be arranged to detect various conditions of the kiln, suchas its temperature and the emission of bluish smoke. Where appropriatethe detectors may make an indication to observers and/or send signals todrivers that will perform the tasks which this application mentioned maybe done manually, such as opening or sealing off certain open ports andintakes.

[0143] While the foregoing description and drawings represent thepreferred embodiments of the present invention, it will be understoodthat various changes and modifications may be made without departingfrom the spirit and scope of the present invention.

What is claimed is:
 1. A method of assembling a portable kiln to turnwood waste into a charcoal, comprising the steps of: nesting componentsof an unassembled portable kiln one into the other, the componentsincluding at least a base and a cover; transporting the unassembledportable kiln to a site of wood waste with a vehicle; removing the basefrom the vehicle and positioning the base on ground at the site;arranging a plurality of air channels about a periphery of the base eachbeing spaced apart from each other; filling the base with wood waste soas to avoid blocking the air channels with the wood waste; and removingthe cover from the vehicle and stacking the cover atop the base.
 2. Amethod as in claim 1, wherein the base includes a bottom section and anupper section, further comprising the steps of: filling the bottomsection with wood waste and stacking the upper section atop the bottomsection, and then filling the upper section with wood waste, thereaftercarrying out the stacking of the cover by stacking the cover atop theupper section.
 3. A method as in claim 2, wherein the bottom and uppersections each have a shelf spaced from their respective peripheraledges, the upper section having a bottom supported on the shelf of thebottom section, the cover having a bottom supported on the shelf of theupper section.
 4. A method as in claim 1, further comprising gatheringthe wood waste at the site before the portable kiln is transported tothe site and continuing to gather more wood waste and bringing more woodwaste to the site after the kiln has been transported to the site.
 5. Amethod as in claim 1, wherein the cover has at least one port, furthercomprising starting a fire at a plurality of locations to burn thewoodwaste inside the base.
 6. A method as in claim 5, wherein the airchannels each have a collar arranged outside the base, furthercomprising positioning smokestacks on at least every other one of thecollars after the woodwaste burns for a period of time.
 7. A method asin claim 6, wherein neighboring ones of the air channels define voidsbetween them, further comprising waiting until a temperature within thebody is suited for carbonization and then closing the voids with asealing material and closing an open end of the air channels whosecollars support the smokestacks so that only the air channels whosecollars are free from supporting the smokestacks permit air flow intothe base.
 8. A method as in claim 6, wherein the cover has ports,further comprising closing the ports and the smokestacks and the airchannels by the time charring is complete.
 9. A method as in claim 6,wherein the collars include a group on which the smokestacks arearranged and a group on which none of the smokestacks are arranged,further comprising moving the smokestacks from the group of the collarswhere the smokestacks are arranged to the group of the collars on whichnone of the smokestacks are arranged during a period of carbonization.10. A method as in claim 6, further comprising creating a reversedrought in which air enters the base through the air channels that arefree of supporting smokestacks and up through a center of the base andcombustion gases are drawn down an outer edge of the base and releasedthrough the smokestacks.
 11. A method as in claim 5, further comprisingallowing combustion of the woodwaste to take place and complete so as tothereafter enter a period of carbonization, compensating when necessaryto ensure that even temperatures are maintained around a circumferenceof the base throughout the period of carbonization, the compensatingincluding partially or completely blocking at least one of the airchannels on a windward side if any and, in an event of water condensingon a hotter side of the base, temporarily blocking the air channels onthe hotter side of the base and uncovering spaces between the airchannels on a cooler side of the base to allow more air flow to enter.12. A method as in claim 6, further comprising cleaning the smokestacksof excessive tar buildup during the period of carbonization that createsa noticeable reduction in a quantity of smoke issuing from thesmokestacks.
 13. A method of using a portable kiln to turn wood wasteinto a charcoal, comprising the steps of: (a) transporting the portablekiln to a site of wood waste; (b) assembling a portable kiln consistingof one bottom section, one upper section and one cover, wherein saidcover contains one or more steam release ports, and wherein both thebottom section and upper section contain a supporting shelf forsupporting successive layers of the portable kiln; (c) filling thebottom section with wood waste to a point where the supporting shelf ofthe bottom section remains exposed; (d) placing the upper section on thesupporting shelf of the bottom section; (e) filling the upper sectionwith wood waste to a point where the supporting shelf of the uppersection remains exposed; (f) placing the conical cylindrical section onthe supporting shelf of the upper section; (g) opening said one or moresteam release ports; and (h) lighting the portable kiln.
 14. A method asin claim 13, where the portable kiln can be transported such that thecover can fit within the upper section.
 15. A method as in claim 13where the portable kiln can be transported such that the upper sectioncan fit within the lower section.
 16. A method as in claim 13 wheresteps (a) through (g) occur at the wood waste site.
 17. A portableapparatus for making charcoal comprising: a base having an open top andbottom, the base also having a shelf that extends about a periphery ofan interior of the base; a plurality of air channels spaced apart fromeach beneath the base; a cover closing the open top and resting on theshelf, the cover having at least one port, the cover having a bottomthat defines an outside area dimension, the base having a bottom thatencloses an inside area dimension that is larger than the outside areadimension defined by a bottom of the cover, the shelf defining an insidearea dimension that is smaller than the outside area dimension definedby the bottom of the cover, the cover having a distance in a directionof elevation that is smaller than a distance of elevation of the base.18. The apparatus as in claim 17 wherein the base includes a bottomsection and an upper section, the upper section having the shelf, thebottom section having a further shelf on which is supported the uppersection.
 19. The apparatus as in claim 17 wherein the base iscylindrical in shape.
 20. The apparatus as in claim 17 wherein the coveris conical.
 21. The apparatus as in claim 17, wherein the air channelshave collars, further comprising a plurality of smokestacks fitted onevery other one of the collars.
 22. A portable apparatus for makingcharcoal comprising: a base having an open top and bottom, the base alsohaving a shelf that extends about a periphery of an interior of thebase; a cover configured to close the open top when resting on theshelf, the cover having at least one port, the cover having a bottomthat defines an outside area dimension, the base having a bottom thatencloses an inside area dimension that is larger than the outside areadimension defined by a bottom of the cover, the shelf defining an insidearea dimension that is smaller than the outside area dimension definedby the bottom of the cover, the cover having a distance in a directionof elevation that is smaller than a distance of elevation of the base.23. The apparatus as in claim 22, further comprising a vehicle on whichis arranged the base with the cover arranged within confines of thebase.
 24. An apparatus as in claim 23, wherein the base has an uppersection and a bottom section, the upper section having the shelf, thebottom section having a further shelf on which a bottom of the uppersection is configured to be supported when stacked on top, the uppersection being within confines of the bottom section on the vehicle andthe cover being within confines of the upper section on the vehicle, thebottom section having a dimension in an elevation direction that islarger than a dimension of in the elevation direction of the uppersection.